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Moon LRO South Pole DEM Verification and Validation Report

This report describes a Digital Elevation Model (DEM) generated from Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Cameras (NAC) stereo pairs over the lunar south pole and provides a comparison to the Lunar Orbiter Laser Altimeter (LOLA) 5-m DEM (Neumann, 2010.) The methodology used to generate this DEM was changed from our previous procedures of registering the LROC NAC images to LOLA track data (Tran and others, 2010; Rosiek and others; 2012, Rosiek and others, 2013.) For this project we added registration of the LROC NAC images to the LOLA DEM. This change was possible and needed because the LOLA 5-m DEM is dense enough to support registration to the DEM and the number of LOLA track points is so large that we were unable to download all the LOLA altimeter points for the area being mapped and be efficient in using them. We only downloaded the altimeter points for several small patches throughout the area covered by the images. The SOCET SET®* (de Venecia and others, 2005; Zhang and others, 2006) sensor model was updated to accommodate images that crossed the pole, and other software modifications were made to map images that were captured while the spacecraft was rotating. The resulting LROC NAC DEM has a post spacing of 4 m and contains 66,555,500 grid cells that cover an area of about 1,065 sq. km. The image coverage used to produce this DEM is provided in Figure 1. A color hillshade representation is provided in Figure 13 with a comparison to the LOLA DEM provided in Figure 14. A slope map is provided in Figure 23 and a comparison to the LOLA DEM is provided in Figure 24. The LROC NAC DEM improves upon the LOLA DEM in that the LROC NAC DEM is smoother and has been edited for major blunders. Within the LROC NAC DEM there are still errors due to seams of 1 – 5 m between the stereomodels. This is probably caused by spacecraft motion that is un-modeled and we provide recommendations in the conclusion section on research that may minimize these seams. Also, in areas of the LROC NAC DEM where the images are in shadow or along the edges of DEM there might be erroneous data that we did not catch during the editing process. Most of the differences (56%) between the LROC NAC and LOLA 5-m Grid DEM are within the expected difference of 2 m. The remainder of the differences can be attributed to seams between stereomodels, errors in shadow masking of the LROC NAC DEM, and errors in the LOLA 5-m Grid DEM caused by offsets in the LOLA track data; this last reason probably accounts for most of the differences. Slope values above 30° are unusual and might be erroneous; within the LROC NAC DEM only 0.78% of the slopes are above 30° and within the LOLA DEM there are 4.57% of the slope values above 30°.